Curvable pipe section

ABSTRACT

A drill string section which may be used with its longitudinal axis straight or curved is made up of two or more coaxial tubular members, each bent in a continuous curve over part of its length, one rotatable within the other between selected rotational relative positions so that each member may strain the other toward straightness when their independent centers of curvature are on opposite sides of their mutual centerline with means to induce such relative rotation upon command. Alternately, two coaxial equally curved tubular members, as an assembly, inside a normally straight drill string section, or housing, is caused to tend to curve to impart a strained curvature to the housing. The inner assembly may be held stationary relative to earth while the housing is rotated, the result when the inner assembly is curved being a curved drill string section with its longitudinal axis lying in a stationary plane while the drill string is rotated about its longitudinal axis. Used in either configuration, the drill pipe section may be inserted into a well bore straight and used straight with the ability to induce the curve as needed for laterally deflecting the well bore as it is being drilled.

United States Patent 1 J eter July 8,1975

[75] Inventor:

[52] US. Cl 175/74; 175/75 [51] Int. Cl E21b 7/08 [58] Field of Search175/73, 74, 75, 76, 61; 285/118, 184; 138/140, 148

[56] References Cited UNITED STATES PATENTS 2,621,894 12/1952 Zublin175/75 X 2,631,820 3/1953 Zublin 175/75 3,637,032 l/l972 .leter 175/733,743,034 7/1973 Bradley 175/61 3,767,836 10/1973 Gels et a1. 175/61 XPrimary ExaminerDavid H. Brown [57] ABSTRACT A drill string sectionwhich may be used with its longitudinal axis straight or curved is madeup of two or more coaxial tubular members, each bent in a continuouscurve over part of its length, one rotatable within the other betweenselected rotational relative positions so that each member may strainthe other toward straightness when their independent centers ofcurvature are on opposite sides of their mutual centerline with means toinduce such relative rotation upon command. Altemately, two coaxialequally curved tubular members, as an assembly, inside a normallystraight drill string section, or housing, is caused to tend to curve toimpart a strained curvature to the housing. The inner assembly may beheld stationary relative to earth while the housing is rotated, theresult when the inner assembly is curved being a curved drill stringsection with its longitudinal axis lying in a stationary plane while thedrill string is rotated about its longitudinal axis. Used in eitherconfiguration, the drill pipe section may be inserted into a well borestraight and used straight with the ability to induce the curve asneeded for laterally deflecting the well bore as it is being drilled.

5 Claims, 6 Drawing Figures P'A'TEF ITEH JUL 8 ms SHEET 10F 2 FIG.1

was

SHEET 20F 2 3333,523

MFHTEHJUL 8 ms FIGS FIG5 CURVABLE PIPE SECTION In the drilling of holes,it is often desirable or necessary to control the direction in which thebore is progressing as it is being drilled. In well drilling it iscustomary to use a bent section in the drill string just above adrilling motor driving the drilling bit to encourage it to movelaterally, deflecting the bore as drilling progresses. Normally there isan abrupt bend inserted between straight sections. This places anabnormal strain on drilling equipment both in action and when beingplaced in the well bore. Some devices are being used which are insertedinto the well bore straight and subsequently bent by a hinging action.Such devices cannot be rotated when bent. The US. Pat. No. 3,637,032,issued Jan. 25, 1972, has a hinged joint that can be rotated, but aconsiderable amount of machinery is involved and the bend is a pointbend rather than a curve.

The term curvable as used herein is defined as bendable with bendingoccurring normally, but not exclusively, within the elastic limit of thematerial being bent in a reasonably uniform amount per unit of lengthover the length being bent.

The device of this invention may be inserted into a bore hole straightand caused to curve when needed. The device may also be usednon-rotative above a drilling motor or it may be used in an alternateembodiment with the curved centerline being a line in a stationary planerelative to earth while the drill string rotates in normal drillingpractice. The device may be used end-to-end making up a series ofcurvable sections, each being curved in turn as the point of departureis reached as drilling progresses resulting in a long continuous curvecomprising any desired degree of total curvature.

It is an object of this invention to provide a device to curve anduncurve a drill string section in a long, reasonably uniform curve afterit is inserted in a well bore.

It is another object of this invention to provide a device to curve anduncurve a length of drill pipe through a command sent down from thesurface of the earth.

It is another object of this invention to provide a curve inducingdevice that may be held stationary relative to earth even though thedrill string in which it is installed may rotate or oscillateindependently of the curve inducing device.

It is a further object of this invention to provide a device to inducerelative rotation of the curve inducing members to control theend-to-end direction change in the centerline of the curve inducingsection.

It is another object of this invention to provide a drill string sectionthat can be used with other similar sections in series to form a long,continuous curve in the well bore and follow through such curvature withminimal strain.

It is yet another object of this invention to provide a device tocontrol the amount of curvature induced into the drill string inresponse to needs as determined by a programmed instrument package inthe vicinity of the drill bit.

It is still a further object of this invention to provide a devicecapable of inducing the elected amount and orientation of curvature in adrill string upon commands transmitted from the surface throughcommunication means contained in the drill string.

These and other objects, advantages and features of this invention willbe apparent to those skilled in the art from a consideration of thisspecification, including the attached drawings and appended claims.

FIG. 1 is an elevation of an uncurved assembly device of this inventioninserted between the lower end of a drill string and a downhole motordriving a drill bit typical of normal earth boring operations.

FIG. 2 is the same as FIG. 1 except that the curvable section of thisinvention is shown in the curved configuration and has caused theadvancing drill bit to deflect laterally, changing the direction inwhich the well bore is being drilled.

FIG. 3 is a longitudinal section of the curvable section shown in theuncurved configuration.

FIG. 4 is a longitudinal section of the curvable section shown in thecurved configuration.

FIG. 5 is a longitudinal section of a curvable device that can be usedin rotary drilling with or without a downhole motor.

FIG. 6 is the same as FIG. 5 but shown in the curved configuration.

In the anticipated down hole operation, as shown in FIG. 1, the deviceof this invention 2 is attached to drill string 1 at the top and todownhole motor 3 at the bottom. A down hole drilling motor has an outputshaft 4 rotating a drilling bit 5. Although the downhole motor outputshaft rotates relative to the drill string, in most cases it isdesirable to rotate drill string 1 while drilling to avoid stuck drillstring and to condition the hole. With device 2 in the straightconfiguration drill string rotation is practical.

To change the direction of the bore hole as it is being drilled, device2 is caused to curve along its longitudinal axis by processes to bedescribed later so that the drill bit will be urged to deflect laterallyas shown in FIG. 2. During this activity, The drill string is normallyoriented relative to earth by one of a variety of currently used meansso that the lateral deflection will be in a preferred direction and, ofcourse, the drill string will not be rotated.

In accordance with the device of this invention the basic act ofchanging the curvature of the longitudinal axis of a drill stringsection requires only two structural load bearing members. As shown inFIG. 4 an outer member 12 is part of the drill string, being attachedabove by means not shown to the upwardly extending drill string andbeing attached below by means not shown to the downwardly extendingdrill string. The midsection of member 12 is tubular and has an inherentcurve in its longitudinal axis. Inner member 11 is axially supported forrotation within the bore of member 12 and has generally the same axialcurvature and flexure characteristics as member 12 in the length ofmember 12 that its occupies. Actuator 6 can rotate member 11 forrelative rotational positioning within member 12 about their mutuallongitudinal axis. In this embodiment, the outside diameter of member 11is only slightly smaller than the midsection bore diameter of member 12so that the longitudinal axis of both members generally coincide.Rotation of degrees will change the radius of curvature of the devicebetween opposite extremes. Intermediate curvature changes require lessrelative motion. It is preferable that at one extreme of the range ofpossible axial curvatures the device approaches straightness, as shownin FIG. 3. In referring to FIG. 4, assume that inner member 11 can beinserted into the bore of outer member 12 since both have approximatelythe same curvature and the bore of member 12 clears the major diameterof member 11. Bearing balls are inserted through a plug (not shown) toaxially retain member 11 in position within member 12. FIG. 4 then showsmembers 11 and 12 in the unstrained condition. The curvature of theassembly then approximates the individual axial curvature of member 11and member 12.

FIG. 3 shows the assembly after actuator 6 has rotated member 11 about180 within member 12. Assume equal curvature of member 11 and member 12as produced and equal stiffness of member 11 and member 12. The 180rotation places the center of curvature of member 11 and member 12 onopposite sides of their mutual centerline. Both members tend to curve inopposite directions and each places a bending load on the other andhaving the same stiffness characteristics, the imposed bending loads areequal. Having the same flexure qualities, member 11 and member 12 strainthe same amount resulting in forcing both tubes to be strained to andconstrained in a straight configuration. Radial loading between member11 and member 12 is shown to be carried by full length bearing surfaces13 being the outside of member 11 and the inside of member 12.

In straight or curved application, drilling fluid flows down the drillstring bore, around actuator 6, between actuator support spider ribs 7and into throat areas 9, into the bore 14 and on through lower terminus15 to which the lower drill string apparatus is attached. Actuator 6receives instructions and power from other devices such as theDirectional Drilling Apparatus No. 3,637,032, issued Jan. 25, 1972, orperhaps the Steerable Drill String, No. 3,743,034, issued July 3, 1973.

Referring to FIG. 5, the threaded devices necessary to assemble theparts shown have been omitted to simplify the description of thefunction of invented features. Assume that inner member 30 can beinstalled in outer member 29 along with actuator 25, and assume furtherthat outer member 29 can be installed in housing along with orientingmotor 21.

Housing 20 is part of a drill string being attached at the top by meansnot shown to the upwardly extending drill string and being attached atthe bottom by means not shown to the downwardly extending drill string.

Motor 21 is any suitable continuously rotatable motor capable ofrotating shaft 23 continuously in either direction at any needed speedand can orient and hold shaft 23 relative to a set of coordinates notnecessarily related to housing 20. The motor 21 may be controlled by theaforesaid patents.

Actuator 25 may be the same as actuator 6 of FIG. 3 and FIG. 4. Actuator25 may receive control and power through shaft 23 of motor 21 from thesame means controlling motor 21.

As manufactured, housing 20 will be straight as shown in FIG. 5 andmember 29 and member 30 will be equally curved as shown in FIG. 6. Aftermember 30 is inserted into member 29 they will be rotated about 180relative to each other and then will be straight as described aboverelative to FIG. 3 and FIG. 4. The straight assembly will then beinserted into the bore of housing 20. Axial relationship between member29 and member 30 is controlled by thrust bearings in actuator 25 by wayof shaft 27. Axial position of member 29 within housing 20 is controlledby thrust bearings (not shown) in motor 21 by way of shaft 23.

In normal straight rotary drilling, the straight configuration of FIG. 5would be appropriate. Member 29 and member 30 are strained tostraightness and held in that condition. Motor 21 is inactive and allshown are stationary relative to housing 20.

When being used to urge the drill bit to move laterally to change thewell bore direction actuator 25 rotates member 30 about within member29. The inner assembly comprising members 29 and 30 will then tend tocurve within housing 20. The normally straight housing 20 will resistthe curving forces of the inner assembly and they will not fully reachtheir unstrained inherent curvature, but housing 20 will be curved tosome extent by such forces. Motor 21 is then activated to orient theinner assembly so that the resulting curve lies in a selected planerelative to earth. This plane is selected by one of the aforementionedpatents or other means.

The curvature relationships and the relative rotation of the curvedelements are mentioned herein for discription convenience and are not tobe regarded in a limiting sense. There are many possible combinations ofradius of curvature, angle of relative rotation and flexurerelationships.

Housing 20 may rotate or oscillate relative to earth without changingthe plane of curvature of the assembly relative to earth because motor21 rotates member 29 within the bearing surfaces 32. Bearing 32 maycomprise the outer surface of member 29 and the inner surface of housing20.

Drilling fluid is delivered down the bore of the drill string, flowsaround motor 21, between spiders 22, through 26, through 28, down bore31 and out bore 34.

The invention having been described, what is claimed 1. A curvable drillpipe section carried by a pipe string extending into a well bore thatcan be actuated to change the radius of curvatures of the longitudinalcenterline of the section comprising; an inherently curved tubular outermember, an inherently curved cylindrical inner member axially supportedand radially constrained within the bore of said tubular outer membersuch that the longitudinal centerline of the inner member is generallycoincident with the longitudinal centerline of said outer member forrelative rotation and relative rotational positioning within said outermember, means to rotate said inner member relative to said outer member,means to lock said inner member in selected rotational position relativeto said outer member, so that by changing the rotational position ofsaid inner member relative to said outer member said inner member willstrain said outer member to change the curvature of the longitudinalcenterline of the section.

2. The device of claim 1 in which said inherently curved tubular outermember and said inherently curved cylindrical inner member have suchinherent radius of curvature of their longitudinal centerlines and suchflexure characteristics that in at least one relative rotationalposition their mutual centerline is generally straight.

3. A curvable drill string section carried by a pipe string extendinginto a well bore that can be actuated to change the radius of curvatureof the longitudinal centerline of the section comprising; a housinghaving a generally cylindrical longitudinal opening, means at each endto attach said housing to pipe string components in end-to-endrelationship, an inherently curved outer tubular member axially andradially supported within the opening of said housing such that thelongitudinal centerline of said outer member generally coincides withthe longitudinal centerline of said housing for rotation within saidopening, an inherently curved cylindrical inner member axially andradially supported within the bore of said outer tubular member suchthat its longitudinal centerline generally coincides with thelongitudinal centerline of said outer member for rotational movement androtational positioning relative thereto, means to rotationally move androtationally position said inner member relative to said outer member,means to rotate said inner and outer members as an assembly relative tosaid housing, whereby said inner member can be selectively rotationallypositioned within said outer member to urge the centerline of said outermember to a selected curvature and said assembly can be rotated relativeto said housing so that as said housing is rotated by the pipe stringrelative to earth the centerline of said assembly can be caused to liein a plane independent of said housing so that said housing is urged bysaid assembly to curve along a centerline in said plane as said housingis rotated about said centerline to cause a drill bit attached theretoto tend to deflect laterally as drilling takes place.

4. The device of claim 3 in which said outer inherently curved memberand said inherently curved inner member have such intrinsic axialcurvatures and flexure characteristics that in at least one relativerotational position therebetween their mutual centerline will bestrained to approximate straightness.

5. A curvable drill string section carried by a pipe string extendinginto a well bore that can be actuated to change the radius of curvatureof the longitudinal centerline of the section comprising; a housinghaving a generally cylindrical central longitudinal opening, means ateach end to attach said housing to pipe string components in end-to-endrelationship, an inherently curved outer tubular member axially andradially supported within the opening of said housing such that thelongitudinal centerline of said outer member generally coincides withthe longitudinal centerline of said housing for rotation within saidopening, an inherently curved cylindrical inner member axially andradially supported within the bore of said outer tubular member suchthat its longitudinal centerline generally coincides with thelongitudinal centerline of said outer member for rotational movement androtational positioning relative thereto, means to rotationally move androtationally position said inner member relative to said outer member,means to rotate said inner and outer members as an assembly relative tosaid housing and to rotationally position and assembly relative to anearth related coordinate system, whereby said inner member can beselectively rotationally positioned within said outer member to urge thecenterline of said outer member and said housing to a selected curvatureand said assembly can be rotated relative to said housing so that assaid housing is rotated by the pipe string relative to earth thecenterline of said assembly can be caused to lie in a selected planeindependent of said housing so that said housing is urged by saidassembly to curve along a centerline in said plane as said housing isrotated about said centerline to cause a drill bit attached thereto totend to deflect laterally in a selected direction as drilling takesplace.

1. A curvable drill pipe section carried by a pipe string extending intoa well bore that can be actuated to change the radius of curvatures ofthe longitudinal centerline of the section comprising; an inherentlycurved tubular outer member, an inherently curved cylindrical innermember axially supported and radially constrained within the bore ofsaid tubular outer member such that the longitudinal centerline of theinner member is generally coincident with the longitudinal centerline ofsaid outer member for relative rotation and relative rotationalpositioning within said outer member, means to rotate said inner memberrelative to said outer member, means to lock said inner member inselected rotational position relative to said outer member, so that bychanging the rotational position of said inner member relative to saidouter member said inner member will strain said outer member to changethe curvature of the longitudinal centerline of the section.
 2. Thedevice of claim 1 in which said inherently curved tubular outer memberand said inherently curved cylindrical inner member have such inherentradius of curvature of their longitudinal centerlines and such flexurecharacteristics that in at least one relative rotational position theirmutual centerline is generally straight.
 3. A curvable drill stringsection carried by a pipe string extending into a well bore that can beactuated to change the radius of curvature of the longitudinalcenterline of the section comprising; a housing having a generallycylindrical longitudinal opening, means at each end to attach saidhousing to pipe string components in end-to-end relationship, aninherently curved outer tubular member axially and radially supportedwithin the opening of said housing such that the longitudinal centerlineof said outer member generally coincides with the longitudinalcenterline of said housing for rotation within said opening, aninherently curved cylindrical inner member axially and radiallysupported within the bore of said outer tubular member such that itslongitudinal centerline generally coincides with the longitudinalcenterline of said outer member for rotational movement and rotationalpositioning relative thereto, means to rotationally move androTationally position said inner member relative to said outer member,means to rotate said inner and outer members as an assembly relative tosaid housing, whereby said inner member can be selectively rotationallypositioned within said outer member to urge the centerline of said outermember to a selected curvature and said assembly can be rotated relativeto said housing so that as said housing is rotated by the pipe stringrelative to earth the centerline of said assembly can be caused to liein a plane independent of said housing so that said housing is urged bysaid assembly to curve along a centerline in said plane as said housingis rotated about said centerline to cause a drill bit attached theretoto tend to deflect laterally as drilling takes place.
 4. The device ofclaim 3 in which said outer inherently curved member and said inherentlycurved inner member have such intrinsic axial curvatures and flexurecharacteristics that in at least one relative rotational positiontherebetween their mutual centerline will be strained to approximatestraightness.
 5. A curvable drill string section carried by a pipestring extending into a well bore that can be actuated to change theradius of curvature of the longitudinal centerline of the sectioncomprising; a housing having a generally cylindrical centrallongitudinal opening, means at each end to attach said housing to pipestring components in end-to-end relationship, an inherently curved outertubular member axially and radially supported within the opening of saidhousing such that the longitudinal centerline of said outer membergenerally coincides with the longitudinal centerline of said housing forrotation within said opening, an inherently curved cylindrical innermember axially and radially supported within the bore of said outertubular member such that its longitudinal centerline generally coincideswith the longitudinal centerline of said outer member for rotationalmovement and rotational positioning relative thereto, means torotationally move and rotationally position said inner member relativeto said outer member, means to rotate said inner and outer members as anassembly relative to said housing and to rotationally position andassembly relative to an earth related coordinate system, whereby saidinner member can be selectively rotationally positioned within saidouter member to urge the centerline of said outer member and saidhousing to a selected curvature and said assembly can be rotatedrelative to said housing so that as said housing is rotated by the pipestring relative to earth the centerline of said assembly can be causedto lie in a selected plane independent of said housing so that saidhousing is urged by said assembly to curve along a centerline in saidplane as said housing is rotated about said centerline to cause a drillbit attached thereto to tend to deflect laterally in a selecteddirection as drilling takes place.